The third generation partnership project (3GPP) has recently initiated the long term evolution (LTE) program to bring new technology, new network architecture, new configuration, and new applications and services to the wireless cellular network in order to provide improved spectral efficiency and faster user experiences. One new item adopted by the LTE program is the mobility tracking area concept, which replaces the former third generation (3G) universal mobile telecommunications system (UMTS) system's location area (LA), registration area (RA) and universal terrestrial radio access network (UTRAN) registration area (URA).
There is only one common tracking area concept defined for radio access network (RAN) and core network (CN) in LTE/system architecture evolution (SAE). The location of an LTE wireless transmit/receive unit (WTRU) that is in an idle state (LTE_IDLE) is known by the network on a tracking area granularity. The goal is to reduce the mobility area management complexities and to reduce the related signaling overhead for the mobility area update whereby, instead of using both the RA/LA and the URA for UMTS, only a tracking area (TA) is used for LTE.
Prior to LTE, due to the second generation (2G) legacy, the 3G UMTS mobility area management has a location area, which includes one or more routing areas. The 3G UMTS also has a URA, which covers one or more UMTS cells. The mobility management involves the URA update, which is administered by a radio resource control (RRC) unit, and the routing area update (RAU) which is administered by the general packet radio service (GPRS) mobility manager (GMM) at the non-access stratum (NAS) protocol stack. The WTRU URA update is triggered by the matching of the current URA identification (URA-ID) with the cell-published URA-ID contents in UMTS system information block (SIB) type 2 (SIB-2). The RAU is triggered by the changing of any one of the public land mobile network identification (PLMN-ID), the location area code (LAC) and the routing area code (RAC). Note that both the LAC and the RAC are published to the cell via SIB-1. The current 3GPP UMTS system information broadcast content is shown in the following Table 1.
TABLE 1WTRUWTRUSystemmode/statemode/stateModificationInformationwhen blockwhen blockSchedulingof SystemAdditionalBlock (SIB)Area scopeis validis readInformationInformationCommentMasterCellIdle mode,Idle mode,SIB_POS = 0Value taginformationCELL_FACH,CELL_FACH,SIB_REP = 8 blockCELL_PCH,CELL_PCH,(FDD)URA_PCH,URA_PCH,SIB_REP = 8, 16,CELL_DCHCELL_DCH32 (TDD)(TDD only)(TDD only)SIB_OFF = 2SchedulingCellIdle mode,Idle mode,Specified by the IEValue tagblock 1CELL_FACH,CELL_FACH,“SchedulingCELL_PCH,CELL_PCH,information” URA_PCH,URA_PCH,in MIBCELL_DCHCELL_DCH(TDD only)(TDD only)SchedulingCellIdle mode,Idle mode,Specified by the IEValue tagblock 2CELL_FACH,CELL_FACH,“SchedulingCELL_PCH,CELL_PCH,information” URA_PCH,URA_PCH,in MIBCELL_DCHCELL_DCH(TDD only)(TDD only)SystemPLMNIdle modeIdle,Specified by the IEValue taginformationCELL_FACH,CELL_FACH,“Schedulingblock type 1CELL_PCH,CELL_PCH,information”URA_PCH,URA_PCHCELL_DCHSystemCellURA_PCHURA_PCHSpecified by the IEValue taginformation“Schedulingblock type 2information”SystemCellIdle mode,Idle mode,Specified by the IEValue taginformation(CELL_FACH,(CELL_FACH,“Schedulingblock type 3CELL_PCH,CELL_PCH,information”URA_PCH)URA_PCH)SystemCellCELL_FACH,CELL_FACH,Specified by the IEValue tagIf System informationinformationCELL_PCH,CELL_PCH,“Schedulingblock type 4 is not block type 4URA_PCHURA_PCHinformation”broadcast in a cell,the connected mode WTRU shall applyinformation inSystem informationblock type 3 inconnected mode.SystemCellIdle mode,Idle mode,Specified by the IEValue tagSystem informationinformation(CELL_FACH,(CELL_FACH,“Schedulingblock type 5bis is block type 5CELL_PCH,CELL_PCH,information”sent instead of and 5bisURA_PCH,URA_PCH,system informationCELL_DCHCELL_DCHblock type 5 in(TDD only))(TDD only))networks thatuse Band IV.SystemCellCELL_FACH,CELL_FACH,Specified by the IEValue tagIf system informationinformationCELL_PCH,CELL_PCH,“Schedulingblock type 6 is not block type 6URA_PCH,URA_PCH,information”broadcast in a cell, CELL_DCHCELL_DCHthe connected mode (TDD only)(TDD only)WTRU shall readSystem informationblock type 5. If some of the optional IEs are not included inSystem informationblock type 6, the WTRU shall read thecorresponding IEs in System informationblock type 5SystemCellIdle mode,Idle mode,Specified by the IEExpirationinformationCELL_FACH,CELL_FACH,“Schedulingtimer =block type 7CELL_PCH,CELL_PCH,information”MAX(32,URA_PCH,URA_PCH,SIB_REP *CELL_DCHCELL_DCHExpiration(TDD only)(TDD only)TimeFactor)SystemCellIdle modeIdle modeSpecified by the IEValue taginformation(CELL_FACH,(CELL_FACH,“Schedulingblock typeCELL_PCH,CELL_PCH,information”11URA_PCH,URA_PCH)CELL_DCH)SystemCellCELL_FACH,Idle mode,Specified by the IEValue tagIf system informationinformationCELL_PCH,CELL_FACH,“Schedulingblock type 12 is not block typeURA_PCH,CELL_PCH,information”broadcast in a cell, 12CELL_DCHURA_PCHthe connected mode WTRU shall readSystem informationblock type 11. If some of the optional IEs are not included in System informationblock type 12, the WTRU shall read the correspondingIEs in Systeminformationblock type 11.SystemANSI-41informationblock type13SystemThis systeminformationinformation block block typeis used in 3.84 Mcps 14TDD mode only.SystemCellIdle Mode,Idle Mode,Specified by the IEValue taginformationCELL_FACH,CELL_FACH,“Schedulingblock typeCELL_PCH,CELL_PCH,information”15URA_PCHURA_PCHSystemEquivalentIdle Mode,Idle Mode,Specified by the IEValue tagFor this systeminformationPLMNCELL_FACH,CELL_FACH,“Schedulinginformation block block typeCELL_PCH,CELL_PCH,information”there may be 16URA_PCH,URA_PCHmultiple occurrences.CELL_DCHThis systeminformation block is also valid while inGSM/GPRS.SystemThis systeminformationinformationblock typeblock is used in17TDD mode only.SystemCellIdle mode,Idle mode,Specified by the IEValue tagInformationCELL_FACH,CELL_FACH,“SchedulingBlock typeCELL_PCH,CELL_PCH,information”18URA_PCH,URA_PCHCELL_DCH
While the previously employed NAS RAU procedure and the RRC URA update procedure will no longer apply, a new LTE tracking area update (TAU) procedure and its related LTE SI, operating procedures and tasks in various protocol levels and system levels will have to be defined.
Given the conceptual and architectural change, the LTE system information will have to reflect these changes and also be organized to facilitate the optimization of better WTRU operation and overall system resource utilization.